Summary Ants alter soil structure when making their nests and the fresh soil aggregates brought to the surface become available for erosion. However, the effects of burrowing activities of ants on soil hydrological processes are unclear. In this study, the effects of Tetramorium caespitum, Messor aciculatus and Camponotus japonicus nests on the preferential flow and soil surface hydrologic processes at a small scale were assessed on the Loess Plateau. Soil dyeing and rainfall simulation experiments were conducted to quantify the effects of ants' nests on runoff and water infiltration on slopes. The diameters of nest entrances for T. caespitum, M. aciculatus and C. japonicus were 0.19, 0.33 and 0.56 cm, respectively. The nests of M. aciculatus and C. japonicus promoted water infiltration, resulted in large soil water contents and decreased surface runoff. The turret‐like mounds around the nest entrances made by T. caespitum prevented the formation of soil preferential flow. The depths of dyeing in the soil with M. aciculatus and C. japonicus nests were 32.6 and 49.2 cm, respectively, which were significantly (P < 0.05) deeper than those in the soil with T. caespitum nests (10.0 cm) and no nest (10.3 cm). The unstable soil aggregates made by ants on the soil surface break down easily and encourage the loss of soil sediment. The results show that increasing the ant colonies, especially those with larger bodies, could be considered a strategy to increase water infiltration and soil water content in semiarid areas. In the meantime, the sediment loss cannot be neglected. Highlights This study evaluated the effects of hypogeal ants on soil erosion. The turret‐like mounds of T. caespitum prevent the formation of preferential flow. Ants with larger bodies made bigger nest entrances and resulted in more infiltration. The burrowing activities of ants exacerbate soil erosion.

SummaryWith the advent of large-scale restoration of vegetation in the Loess Plateau, northwest China, there has been an increase in concern about the suitability of loess soil to support permanent vegetation cover. The quantification of soil macropore characteristics could be critical in determining the architecture and hydrological processes of loess soil on the plateau. In this research, we compared the effects of Purple alfalfa (Medicago sativa L.) and Korshinsk peashrub (Caragana korshinskii K.) on the macropore characteristics of a soil profile on the plateau with computed tomography (CT). To achieve this, undisturbed cores of soil were excavated from beneath purple alfalfa (ALF), 22-year-old Korshinsk peashrub (KOP 22 ) and 40-year-old Korshinsk peashrub (KOP 40 ) vegetation types in the Liudaogou watershed for evaluation. The soil macropore characteristics (including macroporosity, largest pore area, amounts of macropores, circularity, surface area density, branch density, junction density and connectivity) were determined with image analysis software. Soil under KOP 22 and KOP 40 treatments had approximately the same amounts of macropores (17 per 6359-mm 2 area), which was three times greater than those under ALF plants. Macroporosity ratios of soil under KOP 22 and KOP 40 plants to that under ALF plants were 2.3 and 3.6, respectively. Compared with KOP 22 , KOP 40 had a larger macroporosity and the largest pore area at the 100-300-mm soil depth. The KOP plants, in particular KOP 40 , apparently improved the macropore network structure of the soil more than ALF. However, the macropores under ALF were much rounder at the 100-300-mm soil depth than those under the other two plants. There was no correlation between macropore characteristics and organic matter content of the soil at 100-400-mm depth. Nevertheless, macroporosity was strongly correlated with the largest pore area. The findings of this research are critical for developing strategies for the restoration of vegetation in the Loess Plateau through improvement of the hydrological process of loess soil.